Phenolic molding compound



Patented Sept. 23, 1952 v H 2,611,759 PHENOLIC MOLDING COMPOUND Charles Henry Hempel, Manitowoc, Wis, assignor to Heresite & Chemical Company, a corporation of Wisconsin No Drawing. Application January 26,1950. Serial No. 140,769 1 Molding powders made of phenolic resins, and

particularly the phenol-formaldehyde resins, are

well known. The present molding powder difiers.

from those previously available in that itmay be made transparent and clear-that is, free'from' gas bubbles- The present material will produce a molded article which is transparent, amber in color or lighter, of great chemical resistance, high dl-electric properties, great resistance to water absorption and of even greater strength than articles previously formed from phenolic resins containing fillers. The product can also be formed by ordinary heat and pressure methods.

The new molding compound and molded product have a wide variety of uses. For example, milking machine parts such as the shells for the infiations may be made transparent so that it may be ascertained readily whether or not the machine is operating properly and when the milk flow has ceased.

The product is produced by methods which differ in two substantial points from the prior art. In the first place, previous molding powders were produced by the use of catalysts, including free ammonia. Thisammonia was present either as ammoninum hydroxid or hexamethylene-tetramin. The present product does not include any compound of ammonia which will liberate ammonia during the subsequent molding process. Instead of ammonium hydroxide, a catalyst is emsodium carbonate or ammonium carbonate is employed. Magnesium carbonate, potassium hydroxide and potassium carbonate may be substituted, but are less desirable. They act much more slowly.

The second fundamental difference between the present product and those of the prior art is that the molding powder is produced directly, rather than by formation of a sheet and subsequent disintegration of the sheet into a powder by grinding or crushing. In the present process the resin after formation is violently agitated under a limited temperature, during which time it passes from the liquid phase, through a syrupy phase, into a lumpy phase and finally into a dry powder. This procedure eliminates over-cured particles which otherwise would speckle the finished product.

The following is an example of the process:

100 parts by weight of phenol and 120 parts of 40% formaldehyde and a small proportion of a 6 Claims. (01. 260-57) catalyst are mixed. Preferably from 5 to 10 parts of sodium carbonate are employed in the above mix. When using ammonium carbonate as the catalyst, the resin may be prepared from 100 parts phenol, 100 parts formaldehyde and'20 parts ammonium carbonate. I

Theingredients are boiled under a reflux condensor until the resin precipitates, the boiling. then being extended for an additional 30 minutes. Thereafter vacuum is applied and the water removed from the resin by heating. During this: phase, the temperature is not allowed to pass materially above C. While 90 C.is the preferred. operating temperature, slightly higher temperatures maybe employed with care, but in no event is it desired to go above'95 C.- During the processa vacuum of 24 inches is preferred and when the temperature of the material reaches 90 C. under such a vacuum, the resin becomes clear. It is then transferred to an agitator which is preferably in the form of a conventional kneader equipped with two agitators revolving. toward each other. The kneader, of course, is equipped with a steam jacket and a hood, the

latter communicating. with a suitable vacuum: pump. A high vacuum is again imposedand the resin brought to theboiling point, but belowthe limiting temperature. Great care is used to see that the temperature is uniform, otherwise local overheating may occur. The' maintenance or boiling conditions throughout the mass, however, is of great assistance in making the temperature uniform.

Samples are taken periodically to determine when the resin has reached the proper stage. When the resin has reached the middle of the 13 stage, the operation is stopped. During this operation in the kneader, the liquid resin becomes a syrup, then forms large lumps and finally becomes a free flowing powder. If the operation is stopped too soon, the resin will not harden under heat and pressure and is also too brittle. If cooked too long, the powder will not flow under heat and pressure. An experienced operator may readily determine from the appearance of, the powder when the proper condition has been reached, and an inexperienced operator may determine the proper stage by taking appropriate samples and testing them.

As soon as the proper stage has been reached, the contents of the kneader are emptied into large pans so that the powder may be spread over a large area and cooled rapidly.

The powder is then molded in the usual manner, although it requires a slightly longer curing time than normal powders. A milking machine inflation shell r sth inch in thickness requires a curing time of approximately ten minutes.

This application is a continuation of my copending application No. 658,227, filed March 29, 1946 and now abandoned.

The foregoing; detailed description has been given fonclearness (if-understanding onlyaand no unnecessary limitations should be understood therefrom as modifications will be obvious to those;

skilled in the art.

I claim:

1. The method of forming ,a-.heat settlngformaldehyde base molding composition which comprises forming phenol formaldehyde resin by reacting the resin-forming ingredients in aqueous solution, and violently agitating the'resin under;

vacuum at a temperature not substantially above 95 C., during which agitation the productzpasses through a syrupy phaseand into a soft lumpy phase, andrthen stopping the agitation and cool-- ln itheresin when it forms into a dry-molding,

powder.

2. Themethod asset forth in claiml inwhioh the..-temperature does not exceed 90 C.

3. The method which comprises forming a:

phenol formaldehyde resin by reaction'oi phenol and;.formaldehyde in aqueous solution, boiling theingredientsunder reflux conditions until the resin: precipitatesapplyinga vacuum to removewaterbut limiting the temperature to 95 C., or less; whereby the resin redissolves toform a clear solution, agitating the cleargsolution under. vacu-' um'and below. 95 0., the vacuum beingsuflicient- 1y =high to causexboillng throughout the mass unum; magnesium and potassium carbonates and potassium hydroxide, and then cooking the mixture underviolent agitation and at a temperature not exceeding 95 C. while applying a'vacu- 4 J um during at least a portion of the agitation, until a dry molding powder forms.

5. The method of forming a phenol formaldehyde composition which comprises mixing 100 parts by weight of phenol with 100 to 120 parts by weight of a 40% solution of formaldehyde in an aqueous solution with: analkaline catalyst of... the class. consisting; of. sodium, ammonium. magnesium and potassium carbonates and potassium hydroxide, boiling the mixture until the resin precipitates, removing the water from the mixture'by'vacuum while maintaining the temperature of the mixture below C. and under a high'vacuum until the resin becomes clear, and then agitating'the-resin under vacuum at an elevated temperature below 95 C. until the resin forms .a" dry 'molding powder.

6. The method of forming a phenol formaldehyde' composition which comprises forming a mixture consisting of parts by weight of phenol lodparts byweight of a 40% aqueous solution of formaldehyde, .20 parts by weight of ammonium carbonate in an aqueous solution. cooking themixture under violent agitation at a temperaturenot exceeding 95 C'. and during the major portion of said agitation subjecting,

the mixture .to a vacuum of 24 inches of mercury.

saidcooking and agitationbeing continued until the mixture becomes a dry molding powder.

CHARLES HENRY HEMPEL.

REFERENCES CITED The following references are of record in. the

file of this patent:

UNITED STATESPATENTS OTHER REFERENCES Morrell, R. S. Synthetic Resins and Plastics,-

1943, page 111.

Laughlin, H; G., Trans. American, Inst. Chem. Engrs; 36, 1940, pages345-355. 

1. THE METHOD OF FORMING A HEAT SETTING FORMALDEHYDE BASE MOLDING COMPOSITION WHICH COMPRISES FORMING PHENOL FORMALDEHYDEHYDE RESIN BY REACTING THE RESIN-FORMING INGREDIENTS IN AQUEOUS SOLUTION, AND VIOLENTLY AGITATING THE RESIN UNDER VACUUM AT A TEMPERATURE NOT SUBSTANTIALLY ABOVE 95* C., DURING WHICH AGITATION THE PRODUCT PASSES THROUGH A SYRUPY PHASE AND INTO A SOFT LUMPY PHASE, AND THEN STOPPING THE AGITATION AND COOLING THE RESIN WHEN IT FORMS INTO A DRY MOLDING POWDER. 